In the related art, a parking assistance device that performs guidance for parking a vehicle (a host vehicle) in an area where parking is allowed has been proposed. In this type of technology, a target position or a guidance route for parking the vehicle is set by detecting surrounding obstacles (for example, another car, walls, curbs, trees, and posts) using a detection unit mounted on the vehicle (for example, an ultrasonic sonar), in such a manner that the obstacles and the vehicle do not interfere (come in contact) with each other.
JP 2014-101101A is an example of the related art.
However, in a case of using an ultrasonic sonar, it is known that there is a characteristic that, since presence of an obstacle (an object) or a distance to the obstacle is detected by performing a detection of a reflected wave, the height of the obstacle cannot be accurately detected. For example, consider a case of parallel parking a vehicle on a road side. In this case, if the obstacle present at a depth side of a parking space is a curb having a short stature, the vehicle can be parked close to the obstacle. On the other hand, if the obstacle present at a depth side is an obstacle having a tall stature such as a wall, a possibility of contact is high. Therefore, it is necessary to park the vehicle by keeping the vehicle away from the obstacle by a certain distance. However, in a case of the parking assistance using the ultrasonic sonar, in performing the detection using the ultrasonic sonar, it is not possible to accurately detect whether the obstacle is an object having a short stature or an object having a tall stature. Therefore, in a case of performing the parking assistance, the vehicle has been guided such that a constant distance is always ensured under the assumption that the obstacle is an object having a tall stature. Therefore, even in a case where the obstacle is a curb and the vehicle can be parked close to the obstacle, the vehicle is guided to a position spaced apart by a certain distance. That is, there has been a case where the vehicle cannot be guided to an appropriate parking position. It is conceivable to separately provide a sensor that can detect the height of an obstacle, but it is not preferable due to a cost increase.